Para-Orthohydrogen Conversion Using a Vortex Tube

ABSTRACT

A para-orthohydrogen conversion device comprises a vortex tube. The vortex tube may include an inlet disposed at a first end of the vortex tube, a catalyst disposed on the interior wall of the vortex tube, a first outlet comprising an opening on the perimeter of a second end of the vortex tube, a stopper disposed at the center of the second end of the vortex tube, and a second outlet disposed on the first end of the vortex tube. A method includes converting parahydrogen to orthohydrogen via the catalyst and rotational force as hydrogen gas moves through the vortex tube such that cooled parahydrogen-rich gas or liquid hydrogen accumulates near the center of the vortex tube.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Appln. No.62/101,593 filed Jan. 9, 2015, entitled “Device to Separate and ConvertOrtho & Parahydrogen Using a Vortex Tube with Catalyst,” which isincorporated by reference in its entirety.

BACKGROUND

Cryogenic refrigeration finds applicability in many fields, includingliquefaction of certain gases, space travel, and fuel storage, forexample. Systems that aid in cryogenic refrigeration operate atcryogenic temperatures, which can be at or below −150° C. To reach suchtemperatures, heat must be removed from the system in question. Typicalrefrigeration systems utilize circulating refrigerants and heat pumps toextract or dissipate heat from the system. These techniques require anumber of moving parts and are often heavy. Moving parts are more proneto breakage at cryogenic temperatures due to the increased brittlenessat such low temperatures. Additionally, heavy refrigeration systems havedisadvantages in certain applications, such as space travel, whereweight can negatively impact fuel requirements and limit travel distanceand time.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items or features.

FIG. 1 illustrates a perspective view of an example para-orthohydrogenconversion device.

FIG. 2 illustrates a cross-sectional side view of an examplepara-orthohydrogen conversion device.

FIG. 3 illustrates a cross-sectional side view of another examplepara-orthohydrogen conversion device with flow indication.

FIG. 4 illustrates a cross-sectional side view of a further examplepara-orthohydrogen conversion device, a portion of which has beenmagnified.

FIG. 5 is a flowchart illustrating an example method by which apara-orthohydrogen conversion device may operate.

FIG. 6 is a flowchart illustrating another example method by which apara-orthohydrogen conversion device may operate.

DETAILED DESCRIPTION Overview

This overview, including section titles, is provided to introduce aselection of concepts in a simplified form that are further describedbelow. The overview is provided for the reader's convenience and is notintended to limit the scope of the implementations or claims, nor theproceeding sections.

This disclosure describes devices and methods for para-orthohydrogenconversion.

As discussed above, cryogenic refrigeration systems operate at cryogenictemperatures, which can be at or below −150° C. Typical refrigerationsystems utilize circulating refrigerants and heat pumps, which require anumber of moving parts that are prone to breakage at cryogenictemperatures. Additionally, such refrigeration systems are heavy, whichcauses disadvantages in certain applications such as space travel.Example devices and methods as described herein alleviate theshortcomings of current cryogenic refrigeration systems by employing avortex tube comprising a catalyst that may convert parahydrogen toorthohydrogen, which is an endothermic reaction that absorbs heat fromthe system. In so doing, the devices described herein may expel heatfrom the vortex tube in the form of orthohydrogen-rich hydrogen gaswhile maintaining cooled parahydrogen-rich hydrogen gas without movingparts, liquid refrigerants, or heavy circulating systems. Furthermore,the para-orthohydrogen conversion devices described herein may be usedto liquefy hydrogen gas.

Before explaining examples of the devices and methods described herein,the following information regarding hydrogen gas and the dynamics ofcentrifugal geometries may be helpful. Diatomic molecules of hydrogen(H₂) have two different spin isomers, orthohydrogen and parahydrogen. Inorthohydrogen molecules, the spins of the two protons are parallel andform a triplet state. In parahydrogen molecules, the spins of the twoprotons are antiparallel and form a singlet state. Due to thesediffering spin states, at standard temperature and pressure, hydrogengas contains approximately 25% parahydrogen and 75% orthohydrogen.Higher percentages of orthohydrogen may be achieved by increasingtemperature or otherwise introducing heat to hydrogen gas. This isprimarily due to the increase in entropy caused by the increasedtemperature, which causes the hydrogen molecules to reach higher energylevels which favor orthohydrogen spin states. Higher percentages ofparahydrogen may be achieved by decreasing temperature or otherwiseextracting heat from hydrogen gas. This is primarily due to the decreasein entropy caused by the decreased temperature, which causes thehydrogen molecules to reach lower energy levels which favor theparahydrogen spin state. As such, in general, orthohydrogen-rich gaswill exist at higher temperatures, while parahydrogen-rich gas willexist at lower temperatures.

Centrifugal geometries, such as vortex tubes, also known asRanque-Hilsch vortex tubes, promote the controlled rotation of gas. Insome applications, compressed air may be rotated within the vortex tube.As the air rotates, the centrifugal nature of the vortex tube allows theair located near the periphery of the vortex tube to move faster thanthe air located near the core or center of the vortex tube. Based on thethermodynamic approach to temperature, at a certain pressure, fastermoving air molecules will have a higher temperature than slower movingmolecules. Thus, in a vortex tube, faster moving air molecules locatednear the periphery of the vortex tube will have a higher temperaturethan the slower moving air molecules located near the center or core ofthe vortex tube. As such, by utilizing a vortex tube, air can beseparated into hot and cold streams.

Moving now to the device described in the present disclosure, the devicemay comprise a vortex tube having a catalyst on at least a portion of aninterior wall of the vortex tube to assist in the conversion ofparahydrogen to orthohydrogen. In some examples, the catalyst may bedisposed on substantially all of an interior surface of the vortex tube,while in other examples the catalyst may be disposed over less than allof the interior surface of the vortex tube. The catalyst may beruthenium, copper, platinum, palladium, manganese, ferric oxide, silver,a rare earth metal, combinations of the foregoing, or any other catalystthat promotes the conversion of parahydrogen to orthohydrogen. Thedevice may also comprise an inlet disposed on a first end of the vortextube. The inlet may receive hydrogen gas, such as for example,pressurized hydrogen gas comprising approximately 50% orthohydrogen andapproximately 50% parahydrogen. The device may also comprise a firstoutlet disposed on a second end of the vortex tube. The first outlet maycomprise an opening on the perimeter of the second end of the vortextube and a stopper disposed at the center of the second end of thevortex tube. The configuration of the first outlet may promote therelease of hydrogen gas situated near the perimeter or periphery of thesecond end of the vortex tube, while hindering or preventing hydrogengas situated near the center or core of the vortex tube from exiting thevortex tube. The shape of the stopper may also direct the hydrogen gassituated near the center or core of the vortex tube back toward thefirst end of the vortex tube. The device may further comprise a secondoutlet disposed on the first end of the vortex tube. The second outletmay promote the release of the hydrogen gas situated near the center orcore of the vortex tube.

In some examples, a method of operating the para-orthohydrogenconversion devices described herein may comprise transferring hydrogengas into a proximal end of a vortex tube. At least a portion of aninterior wall of the vortex tube may comprise a catalyst, such as, forexample, ruthenium, copper, platinum, palladium, manganese, ferricoxide, silver, a rare earth metal, combinations of the foregoing, or anyother catalyst that promotes the conversion of parahydrogen toorthohydrogen. In some examples, the hydrogen gas that is transferredinto the vortex tube may be pressurized and may comprise a predeterminedamount of parahydrogen and orthohydrogen at a certain temperature. Forexample, the hydrogen gas may be pressurized to approximately 50 psi atapproximately 77 K and comprise approximately 50% parahydrogen andapproximately 50% orthohydrogen. It should be noted that a specificpressure and temperature is not required and the temperatures andpressures described herein are for illustration only and are not by wayof limitation. The hydrogen gas may be flowed from the proximal end ofthe vortex tube to the distal end of the vortex tube. As the hydrogengas flows, the hydrogen gas may rotate within the vortex tube. Therotating hydrogen gas may contact the inner wall of the vortex tube,which comprises the catalyst, converting at least a portion of theparahydrogen to orthohydrogen. The reaction of the hydrogen gas with thecatalyst is endothermic, which absorbs heat near the internal wall, orperiphery, of the vortex tube, and creates cooler parahydrogen-rich gasthat rotates near the center or core of the vortex tube.

A first outlet on the distal end of the vortex tube may be configured toallow the orthohydrogen-rich gas rotating on the periphery of the vortextube to exit the vortex tube. The orthohydrogen-rich gas may have ahigher temperature and lower pressure than the hydrogen gas that wasinitially transferred into the vortex tube. For example, theorthohydrogen-rich gas may have a temperature of approximately 120 K andhave a reduced pressure of approximately 14 psi. The first outlet mayalso comprise a stopper or other component that hinders or prevents theparahydrogen-rich gas near the center or core of the vortex tube fromexiting out the first outlet. The stopper may be shaped to promote theflow of parahydrogen-rich gas back toward the proximal end of the vortextube. In some examples, the centerline of the stopper is ported, whichmay promote gas to enter the ported portion of the stopper. In otherexamples, the stopper may have a flat end, as opposed to a pointed end,that may allow the hydrogen gas on the periphery of the vortex tube exitthe tube while creating a stopping point for the hydrogen gas near thecenter or core of the vortex tube. The parahydrogen-rich gas may exitthe vortex tube through a second outlet disposed near the proximal endof the vortex tube. The parahydrogen-rich gas may have a lowertemperature than both the initial hydrogen gas that was transferred intothe vortex tube and the orthohydrogen-rich gas that rotates near theperiphery of the vortex tube. For example, the parahydrogen-rich gas mayhave a temperature of approximately 30 K and may have a pressure similarto the orthohydrogen-rich gas, such as, for example, approximately 14psi.

In some examples, a method of operating the para-orthohydrogenconversion devices described herein may include converting hydrogen gasto liquid hydrogen, also known as liquefaction. For example, hydrogengas may be transferred into the proximal end of a vortex tube, at leasta portion of the inner wall of which may comprise a catalyst. Thehydrogen gas may be pressurized and may enter the vortex tube at a firsttemperature. In some examples, the hydrogen gas may be pre-cooled, suchas by a liquid nitrogen bath. As the hydrogen gas flows from theproximal end of the vortex tube to the distal end, the hydrogen gas mayrotate. The rotation may be caused, at least in part, by the directionof the flow of the hydrogen gas entering the vortex tube. Theparahydrogen in the hydrogen gas may contact the catalyst and beconverted to orthohydrogen, which is an endothermic reaction thatabsorbs heat from the system. The orthohydrogen-rich gas may accumulatenear the periphery of the vortex tube at a temperature higher than thetemperature of the initial hydrogen gas, while parahydrogen-rich gas mayaccumulate near the center or core of the vortex tube at a lowertemperature than the initial temperature of the hydrogen gas, resultingin liquefaction of the parahydrogen-rich gas.

Para-orthohydrogen conversion devices according to this disclosure maybe designed for a variety of applications, such as, for example, removalof heat in cryogenic conditions, cooling of various components of asystem, and/or liquefaction of hydrogen gas.

One or more examples of the present disclosure are illustrated in theaccompanying drawings. Those of ordinary skill in the art willunderstand that the systems and methods specifically described hereinand illustrated in the accompanying drawings are non-limiting examplesand that the scope of these examples is defined solely by the claims.The features illustrated or described in connection with one example maybe combined with the features of other examples. For example, thecompressor described in one example may be included in the systemcomprising the computing devices. Such modifications and variations areintended to be included within the scope of the appended claims.

Additional details are described below with reference to severalexamples.

Example Devices

FIGS. 1-4 illustrate various examples of para-orthohydrogen conversiondevices. The sizes, shapes, and symbols used to describe the variouscomponents of the devices are used for illustration only and should notbe used as limitations of the devices as described herein.

FIG. 1 illustrates a perspective view of an example of apara-orthohydrogen conversion device 100. Device 100 may comprise avortex tube 102. As used herein, the term “vortex tube” means acylindrical tube designed to promote the rotation of air within thetube. The diameter of the vortex tube 102 may vary depending on theapplication and desired amount of hydrogen conversion. For example, alarger-diameter vortex tube 102 may be utilized when conversion of alarge volume of hydrogen gas is desired. The vortex tube 102 may beconstructed of various materials, such as, for example, metal, polymer,or a combination thereof. The vortex tube 102 may be constructed by anumber of methodologies, such as, for example, three-dimensionalprinting and/or metal working (e.g., extrusion, casting, boring, etc.).By way of example, a vortex tube 102 as used in the manner describedherein for para-orthohydrogen conversion may be constructed fromstainless steel, polyvinyl chloride, or other material sturdy enough towithstand the pressure differential as between the interior and exteriorof the vortex tube 102. The vortex tube 102 may comprise an inlet 104disposed on a first end of the vortex tube 102. The inlet 104 may bepositioned such that gas is transferred into the vortex tube 102tangentially or perpendicularly from the flow of gas through the vortextube 102.

The vortex tube 102 illustrated in FIG. 1 may also comprise a firstoutlet 108 disposed on a second end of the vortex tube 102. The firstoutlet 108 may have various shapes and sizes. For example, the firstoutlet 108 may have the same or similar diameter as the vortex tube 102,or the first outlet 108 may have a smaller diameter than the vortex tube102. A stopper 106 may be disposed at or near the center of the secondend of the vortex tube 102. The stopper 106 may be conical shaped, withthe point or vertex of the stopper 106 pointing in toward the vortextube 102. The stopper 106 may be positioned such that only hydrogen gaslocated at or near the periphery of the vortex tube 102 may exit throughthe first outlet 108. In some examples, the stopper 106 may beadjustable, either manually or automatically, such that the stopper 106may move axially into or out of the vortex tube 102. When the stopper106 is adjusted more into the vortex tube 102, the opening between thestopper 106 and the interior wall of the vortex tube 102 may decrease.This decreased opening may decrease the air flow through the firstoutlet 108 and increase pressure within the vortex tube 102. When thestopper 106 is adjusted away from the vortex tube 102, the openingbetween the stopper 106 and the interior wall of the vortex tube 102 mayincrease. This increased opening may increase the air flow through thefirst outlet 108 and decrease pressure within the vortex tube 102. Insome examples, the stopper 106 may include one or more grooves along thecenterline of the stopper 106. The grooves may be received by threadingdisposed on the distal end of the vortex tube 102 and hold the stopper106 in position.

Adjustment of the stopper 106 may also aid in more accurate transferringof orthohydrogen-rich gas from the vortex tube 102. For example, asdescribed above, orthohydrogen-rich gas may accumulate at the peripheryof the vortex tube 102, while parahydrogen-rich gas may accumulate atthe center or core of the vortex tube 102. The thickness of the layer oforthohydrogen-rich gas and the thickness of the layer ofparahydrogen-rich gas within the vortex tube 102 may differ dependingon, for example, the initial concentrations of parahydrogen andorthohydrogen in the hydrogen gas transferred into the vortex tube 102,the pressure within the vortex tube 102, and the initial temperature ofthe hydrogen gas transferred into the vortex tube 102. As such, theorthohydrogen-rich periphery portion or layer may be larger in someapplications or configurations than the orthohydrogen-rich peripheryportion or layer in other applications or configurations. The stopper106 position may be adjusted to account for such variances.

The stopper 106 may also hinder or prevent the parahydrogen-rich gas ator near the center of the vortex tube from exiting through the firstoutlet 108. Instead, the stopper 106 may promote the parahydrogen-richgas to flow back toward the first end of the vortex tube 102. A secondoutlet 110 may be disposed on the first end of the vortex tube 102 andmay be positioned to accept the parahydrogen-rich gas flowing toward thefirst end of the vortex tube 102. The second outlet 110 may bepositioned at or near the center of the vortex tube 102, where theparahydrogen-rich gas is flowing.

FIG. 2 illustrates a cross-sectional side view of an example of apara-orthohydrogen conversion device 200. The cross-section shown inFIG. 2 is made at or near the center of device 100 such that the inlet,first outlet, second outlet, and vortex tube are essentially split inhalf. Device 200 may comprise the same or similar components as device100. For example, device 200 may comprise a vortex tube 202, an inlet204, a first outlet 208, a second outlet 212, and a stopper 210. Device200 may also comprise a catalyst 206 (shown as the shaded portion ofFIG. 2). The catalyst 206 may comprise the material, or a portionthereof, that the vortex tube 202 is constructed of, and/or the catalyst206 may comprise a coating disposed on the interior wall of the vortextube 202. The catalyst 206 may be disposed on the entire interior wallof the vortex tube 202, or only a portion (i.e., less than all) thereof.The catalyst 206 may comprise ruthenium, copper, platinum, palladium,manganese, ferric oxide, silver, a rare earth metal, combinations of theforegoing, or any other catalyst that promotes the conversion ofparahydrogen to orthohydrogen.

Device 200 may also comprise insulation 214, which may partially orcompletely cover an outer circumferential surface of the vortex tube202. In some examples, the insulation may be constructed of one or morematerials that hinder the exchange of heat between the interior andexterior of the vortex tube 202. The insulation 214 may comprise one ormore layers, and when comprising multiple layers, the layers may be madeof the same or differing materials. For example, the insulation 214 maycomprise multi-layer insulation (MLI), silica-aerogel, spray-foam,vacuum, etc.

FIG. 3 illustrates a cross-sectional side view of an examplepara-orthohydrogen conversion device 300 that shows the flow of hydrogengas through the device. The cross-section shown in FIG. 3 is made at ornear the center of device 100 such that the inlet, first outlet, secondoutlet, and vortex tube are essentially split in half. Device 300 mayhave the same or similar components as those shown in FIG. 2. Forexample, device 300 may comprise a vortex tube 302, an inlet 304, acatalyst 306, a first outlet 308, a stopper 310, and a second outlet312. Directional arrows have been added to FIG. 3 to show an exampleflow of hydrogen gas through device 300. Starting at the inlet 304,hydrogen gas may be transferred into device 300 from a source, such as,for example, a pressurized hydrogen gas tank. The hydrogen gas may bepressurized, such as, for example, to around 50 psi, and may comprise apredetermined composition of parahydrogen and orthohydrogen, such as,for example, approximately 50% parahydrogen and approximately 50%orthohydrogen. Again, the temperature, pressure, and para-orthohydrogencomposition described in this example are for illustration only and arenot limiting. The hydrogen gas may travel through the inlet 304 and intothe vortex tube 302. As the hydrogen gas enters the vortex tube 302, thehydrogen gas may begin to swirl or otherwise rotate. The rotatinghydrogen gas may travel down the vortex tube 302 toward the first outlet308. As the rotating hydrogen gas travels, at least a portion of thehydrogen gas makes contact with the interior wall of the vortex tube302.

The interior wall of the vortex tube 302 may comprise a catalyst 306,which may convert all or a portion of the parahydrogen gas that contactsthe interior wall into orthohydrogen, creating a layer oforthohydrogen-rich gas at the periphery of the vortex tube 302 via anendothermic reaction. The catalyzed reaction of parahydrogen toorthohydrogen may cause heat to be absorbed in the orthohydrogen-richlayer, which may cause the orthohydrogen-rich layer to rotate morequickly. The unreacted hydrogen gas may accumulate near the center orcore of the vortex tube 302 and may contain more parahydrogen thanorthohydrogen. This parahydrogen-rich layer may have a decreasedtemperature and rotate slower than the orthohydrogen-rich layer. Whenthe hydrogen gas reaches the first outlet 308 of the vortex tube 302,the stopper 310 may allow the orthohydrogen-rich layer near theperiphery of the vortex tube 302 to exit the vortex tube 302, whilehindering or stopping the parahydrogen-rich layer near the center of thevortex tube 302 from exiting the vortex tube 302. The stopper 310 mayredirect the parahydrogen-rich gas back toward the inlet 304. A secondoutlet 312 may be disposed on the end of the vortex tube 302 oppositethe first outlet 308. The parahydrogen-rich gas may exit the vortex tube302 through the second outlet 312 to a holding container or anadditional vortex tube, for example.

FIG. 4 illustrates a cross-sectional side view of an examplepara-orthohydrogen conversion device 400. Device 400 may have the sameor similar components as those shown in FIG. 2. For example, device 400may comprise a vortex tube 402, an inlet 404, a catalyst 406, a firstoutlet 408, a stopper 410, and a second outlet 412. Device 400 may alsocomprise a plurality of grooves 414. The grooves 414 are depicted inFIG. 4 as being semi-circular in shape, or otherwise described asscalloped, however, the grooves 414 may be of various shapes and sizes.The grooves 414 may also be spirals or channels in the interior surfaceof the vortex tube 402. Additionally, each groove 414 may have a uniformshape and size to other grooves 414, or each groove 414 may varyslightly or substantially in shape and size to other grooves 414.Furthermore, the grooves 414 may be indents or etchings in the vortextube 402 or may be raised up from the surface of the interior wall ofthe vortex tube 402. The grooves 414 may increase the surface area ofthe catalyst 406 and provide for a larger number of reaction sites withthe parahydrogen as it flows through the vortex tube 402.

Devices 100-400 may also include controllers and/or sensors (notillustrated) to monitor and control the pressure, temperature, and flowof hydrogen gas through the vortex tube, as well as valves andassemblies to open or close the flow of hydrogen through the inlet,first outlet, and/or second outlet. Additionally, gauges or othermonitoring devices may be used to monitor pressure, temperature, flowrate, and hydrogen isomer content within the vortex tube. For example,para-orthohydrogen composition of vortex tube effluent may be measuredvia hot-wire anemometry.

As described in FIGS. 1-4, various components of devices 100-400 havebeen described as components of certain examples of thepara-orthohydrogen conversion devices described herein. However, itshould be understood that in some examples each component describedherein may be included in any or all of devices 100-400, and theinclusion of a component in one example does not exclude its potentialinclusion in other examples. Additionally, multiples of devices 100-400may be coupled together to form a system that further promotes cryogeniccooling and liquefaction. For example, three para-orthohydrogenconversion devices, such as described herein, may be coupled together.Hydrogen gas may be transferred to a first conversion device and theresulting parahydrogen-rich gas may be transferred to a secondconversion device. The parahydrogen-rich gas may undergo furtherconversion in the second conversion device such that the resultingparahydrogen reaches a temperature that allows for liquefaction of thehydrogen gas. The liquid hydrogen may be transferred from the secondconversion device to a holding tank or other apparatus for storage oruse. The orthohydrogen-rich gas from the first conversion device may betransferred to a third conversion device. The orthohydrogen-rich gas mayundergo further conversion such that a portion of the remainingparahydrogen is converted to orthohydrogen. As such, thepara-orthohydrogen conversion devices disclosed herein may be cascadedto increase cooling and liquefaction.

The devices described in FIGS. 1-4 have been shown to effectivelyconvert parahydrogen to orthohydrogen, which allows for cryogenicrefrigeration and liquefaction without the use of moving parts or heavyliquid circulation systems. These devices may allow for the efficientliquefaction of hydrogen, in some cases at or above 30% efficiency. Theuse of a catalyst, such as described herein, may increase the efficiencyof cryogenic refrigeration and/or liquefaction. For example, a 69%difference in temperature separation between parahydrogen andorthohydrogen was noted in vortex tubes comprising a catalyst versusbare vortex tubes. Fluid flow modules, such as COMSOL computationalfluid dynamics modeling, may be used to optimize flow of hydrogen gasand liquid hydrogen through the vortex tubes as described herein.

The present disclosure may find use with gases other than hydrogen. Forexample, the vortex tube design described herein may be used with gasessuch as deuterium (²D), Tritium (³H), Helium (He), and Neon (Ne). Thesame or substantially the same design described herein may be used tocool or liquefy the above-mentioned gases. The same or similar catalystsmay be used, as well as the same or similar pressures, temperatures, andcomponents of the devices, such as, for example, the vortex tube, firstand second outlet, inlet, and stopper.

Example Methods

FIGS. 5 and 6 illustrate example methods of operating apara-orthohydrogen conversion device, such as described herein. Methods500 and 600 are illustrated as logical flow graphs. The order in whichthe operations or steps are described is not intended to be construed asa limitation, and any number of the described operations can be omitted,modified, or combined in any order and/or in parallel to implementmethods 500 and 600. For example, while FIG. 6 depicts flowing hydrogengas toward the distal end of the vortex tube with hydrogen gas rotatingwithin the vortex tube before the hydrogen gas reacts with the catalyst,method 600 may comprise reacting the hydrogen gas with the catalystbefore or at the same time as the hydrogen gas rotates within the vortextube.

FIG. 5 illustrates a method 500 of operating a para-orthohydrogenconversion device. At block 502, method 500 may comprise transferringhydrogen gas into a proximal end of a vortex tube. In some examples, thetransferred hydrogen gas may be pressurized, such as, for example, toapproximately 50 psi. At least a portion of an interior wall of thevortex tube may comprise a catalyst. In some examples, the catalyst maybe part or all of the material that the vortex tube is constructed from.In other examples, the catalyst may be a coating covering all or aportion of the interior wall of the vortex tube. The hydrogen gas thatis transferred into the proximal end of the vortex tube may compriseorthohydrogen and parahydrogen. In some examples, the composition of thehydrogen gas may be more orthohydrogen than parahydrogen. In otherexamples, the composition of the hydrogen gas may be more parahydrogenthan orthohydrogen. In other examples, the composition of the hydrogengas may be approximately 50% orthohydrogen and approximately 50%parahydrogen.

At block 504, method 500 may comprise flowing the hydrogen gas toward adistal end of the vortex tube. As the hydrogen gas flows, the hydrogengas may rotate within the vortex tube. The rotating hydrogen gas maycreate a vortex such that the hydrogen gas at the exterior or peripheryof the vortex tube rotates more quickly than the hydrogen gas at thecenter or core of the vortex tube.

At block 506, method 500 may comprise reacting hydrogen gas with thecatalyst such that a least a portion of the parahydrogen is converted toorthohydrogen. In some examples, the catalyst may be ruthenium, copper,platinum, palladium, manganese, ferric oxide, silver, a rare earthmetal, combinations of the foregoing, or any other catalyst thatpromotes the conversion of parahydrogen to orthohydrogen. As theparahydrogen in the hydrogen gas contacts the catalyst, the reaction mayproduce an orthohydrogen-rich layer of hydrogen gas near the peripheryof the vortex tube. The orthohydrogen-rich layer may have a highertemperature than the initial hydrogen gas that was transferred into thevortex tube. The reaction may be endothermic, which causes heat to beabsorbed from the overall system into the orthohydrogen-rich layer. Aparahydrogen-rich layer may accumulate near the center or core of thevortex tube. The parahydrogen-rich layer may have a lower temperaturethan the initial hydrogen gas and the orthohydrogen-rich layer. In someexamples, the orthohydrogen-rich layer may comprise more orthohydrogenthan parahydrogen, such as, for example, approximately 75% orthohydrogenand approximately 25% parahydrogen. In some examples, theparahydrogen-rich layer may comprise more parahydrogen thanorthohydrogen, such as, for example, approximately 25% orthohydrogen andapproximately 75% parahydrogen. Although the orthohydrogen-rich portionof the hydrogen gas and parahydrogen-rich portion of the hydrogen gasare described herein as layers, the two portions need not be distinct orseparate. For example, a gradient of parahydrogen to orthohydrogen mayexist in the vortex tube such that at various locations in the vortextube, differing ratios may exist. In general, a greater percentage oforthohydrogen may be present at the periphery of the vortex tube, whilea greater percentage of parahydrogen may be present at the center of thevortex tube. By way of further example, a velocity gradient may exist inthe vortex tube such that gas rotating at the periphery of the vortextube may rotate more quickly than gas rotating at the center of thevortex tube. The gas between the center and periphery may rotate at somespeed between the speed of rotation at the center and the speed ofrotation at the periphery.

At block 508, method 500 may comprise expelling the orthohydrogen-richgas located at or near the periphery of the vortex tube out of thedistal end of the vortex tube. The distal end of the vortex tube maycomprise an outlet with a stopper, which may be adjustable. The stoppermay have a conical shape, which may allow the orthohydrogen-rich gaslocated at or near the periphery of the vortex tube to exit the vortextube while hindering or stopping the parahydrogen-rich gas located at ornear the center of the vortex tube from exiting the vortex tube. Theorthohydrogen-rich gas may exit the vortex tube at a temperature greaterthan the temperature of the initial hydrogen gas that was transferredinto the vortex tube.

At block 510, method 500 may comprise flowing the parahydrogen-rich gaslocated at or near the center or core of the vortex tube toward theproximal end of the vortex tube. The parahydrogen-rich gas may rotatenear the center of the vortex tube as it flows from the distal end tothe proximal end. An outlet disposed at or near the proximal end of thevortex tube may receive the parahydrogen-rich gas and allow theparahydrogen-rich gas to exit the vortex tube. The parahydrogen-rich gasmay exit the vortex tube at a temperature less than the temperature ofthe initial hydrogen gas and the orthohydrogen-rich gas.

All or a portion of the operations of method 500 may be performed atcryogenic temperatures, such as those found in space. The operation ofmethod 500 may result in a cooled amount of parahydrogen-rich gas, whichmay be used to refrigerate a variety of containers and substances. Forexample, the parahydrogen-rich gas may reach 30K (−243° C.) or less.Liquid oxygen, a commonly used rocket propellant, has a freezing pointof approximately 54K and a boiling point at approximately 90K. As such,the parahydrogen-rich gas may be utilized to maintain liquid oxygen in afrozen or liquid state during space travel until the liquid oxygen isneeded for propulsion. By way of further example, liquid hydrogen isalso a commonly used rocket propellant. Liquid hydrogen, however, has atendency to “boil-off” or otherwise vaporize from ambient heatsurrounding the vessel holding the liquid hydrogen. Method 500 may beutilized to direct the vaporized hydrogen gas toward a vortex tube tostart the para-orthohydrogen conversion process. Method 500 may resultin at least a portion of the vaporized hydrogen gas being cooled back toa liquid state. The re-liquefied hydrogen may be reintroduced to theliquid hydrogen holding tank, thus diminishing the adverse effects of“boil-off” Liquefaction is described in more detail below with respectto method 600.

FIG. 6 illustrates a method 600, which may include the same, different,or additional operations as method 500. At block 602, method 600 maycomprise transferring hydrogen gas into a proximal end of a vortex tube.In some examples, the transferred hydrogen gas may be pressurized, suchas, for example, to approximately 50 psi. At least a portion of aninterior wall of the vortex tube may comprise a catalyst. In someexamples, the catalyst may be part or all of the material that thevortex tube is constructed from. In other examples, the catalyst may bea coating covering all or a portion of the interior wall of the vortextube. The hydrogen gas that is transferred into the proximal end of thevortex tube may comprise orthohydrogen and parahydrogen. In someexamples, the composition of the hydrogen gas may be more orthohydrogenthan parahydrogen. In other examples, the composition of the hydrogengas may be more parahydrogen than orthohydrogen. In other examples, thecomposition of the hydrogen gas may be approximately 50% orthohydrogenand approximately 50% parahydrogen.

At block 604, method 600 may comprise flowing the hydrogen gas toward adistal end of the vortex tube. As the hydrogen gas flows, the hydrogengas may rotate within the vortex tube. The rotating hydrogen gas maycreate a vortex such that the hydrogen gas at the exterior or peripheryof the vortex tube rotates more quickly than the hydrogen gas at thecenter or core of the vortex tube.

At block 606, method 600 may comprise reacting at least a portion of thehydrogen gas with the catalyst such that at least a portion of thehydrogen gas converts to liquid hydrogen. In some examples, at least aportion of the parahydrogen in the hydrogen gas may contact the catalystand be converted to orthohydrogen, causing an orthohydrogen-rich layerof hydrogen gas at or near the periphery of the vortex tube. Slowermoving, parahydrogen-rich gas may accumulate at or near the center ofthe vortex tube. The temperature of the parahydrogen-rich gas maydecrease to at or below the boiling point of hydrogen, which may resultin all or a portion of the hydrogen gas changing to a liquid state. Thevortex tube may be positioned such that as liquid hydrogen is formed,gravity may cause the liquid hydrogen to exit the vortex tube, such asthrough an outlet near the proximal end of the vortex tube. In someexamples, such as in space travel application, little or nogravitational pull may be present. In these examples, a stopper, whichmay be conical shaped, may be disposed at or near the distal end of thevortex tube. The stopper may redirect the parahydrogen-rich gas near thecenter of the vortex tube back toward the proximal end of the vortextube, which may comprise an outlet through which the liquid hydrogen mayexit the vortex tube. The liquid hydrogen produced at or near the centerof the vortex tube may comprise more parahydrogen than orthohydrogen,and in some examples, the liquid hydrogen may comprise all parahydrogen.

At block 608, method 600 may comprise transferring a remaining portionof the hydrogen gas out the distal end of the vortex tube. The remainingportion of the hydrogen gas may comprise more orthohydrogen thanparahydrogen and may exit the vortex tube at a temperature greater thanthe initial hydrogen gas transferred into the vortex tube and theparahydrogen-rich gas and liquid hydrogen located at or near the centerof the vortex tube. In some applications, such as space travel, theorthohydrogen-rich gas that exits the vortex tube may be used forheating applications, such as, for example, air conditioning of a livingenvironment and heating of water or other liquids. Theorthohydrogen-rich gas may also be cooled, such as by exposing the gasto temperatures found in space, which may convert all or a portion ofthe orthohydrogen back to parahydrogen. The hydrogen gas may then bereintroduced into the vortex tube for further cryogenic refrigeration orliquefaction purposes.

The term “about” or “approximate” as used in the context of describing arange of volume, pressure, or temperature is to be construed to includea reasonable margin of error that would be acceptable and/or known inthe art.

The present description uses specific numerical values to quantifycertain parameters relating to the innovation, where the specificnumerical values are not expressly part of a numerical range. It shouldbe understood that each specific numerical value provided herein is tobe construed as providing literal support for a broad, intermediate, andnarrow range. The broad range associated with each specific numericalvalue is the numerical value plus and minus 60 percent of the numericalvalue, rounded to two significant digits. The intermediate rangeassociated with each specific numerical value is the numerical valueplus and minus 30 percent of the numerical value, rounded to twosignificant digits. The narrow range associated with each specificnumerical value is the numerical value plus and minus 15 percent of thenumerical value, rounded to two significant digits. These broad,intermediate, and narrow numerical ranges should be applied not only tothe specific values, but should also be applied to differences betweenthese specific values.

Furthermore, this disclosure provides various example implementations,as described and as illustrated in the figures. However, this disclosureis not limited to the examples described and illustrated herein, but canextend to other examples, as would be known or as would become known tothose skilled in the art. Reference in the specification to “oneexample,” “this example,” “these examples,” or “some examples” meansthat a particular feature, structure, or characteristic described isincluded in at least one example, and the appearances of these phrasesin various places in the specification are not necessarily all referringto the same example.

CONCLUSION

Although the disclosure describes examples having specific structuralfeatures and/or methodological acts, it is to be understood that theclaims are not necessarily limited to the specific features or actsdescribed. Rather, the specific features and acts are merelyillustrative of some examples that fall within the scope of the claimsof the disclosure.

What is claimed is:
 1. A method comprising: transferring hydrogen gasinto a proximal end of a vortex tube, at least a portion of an interiorwall of the vortex tube comprising a catalyst, wherein the hydrogen gascomprises orthohydrogen and parahydrogen; flowing the hydrogen gastoward a distal end of the vortex tube, the hydrogen gas rotating withinthe vortex tube as the hydrogen gas flows toward the distal end;reacting the hydrogen gas with the catalyst such that at least a portionof the parahydrogen is converted to orthohydrogen; expellingorthohydrogen-rich hydrogen gas from the distal end of the vortex tube;and flowing parahydrogen-rich hydrogen gas out the proximal end of thevortex tube.
 2. The method of claim 1, wherein the hydrogen gastransferred into the proximal end of the vortex tube comprisesapproximately 50% orthohydrogen and approximately 50% parahydrogen. 3.The method of claim 1, wherein the orthohydrogen-rich hydrogen gascomprises more orthohydrogen than parahydrogen.
 4. The method of claim1, wherein the orthohydrogen-rich hydrogen gas comprises approximately75% orthohydrogen and approximately 25% parahydrogen.
 5. The method ofclaim 1, wherein the parahydrogen-rich hydrogen gas comprises moreparahydrogen than orthohydrogen.
 6. The method of claim 1, wherein theparahydrogen-rich hydrogen gas comprises approximately 75% parahydrogenand approximately 25% orthohydrogen.
 7. The method of claim 1, whereinthe hydrogen gas transferred to the vortex tube comprises pressurizedhydrogen gas.
 8. The method of claim 1, wherein the catalyst comprisesruthenium, copper, platinum, palladium, manganese, ferric oxide, silver,a rare earth metal, or a combination thereof.
 9. The method of claim 1,wherein the method is performed at or below approximately 123 K.
 10. Themethod of claim 1, wherein the catalyst coats the at least the portionof the interior wall of the vortex tube.
 11. The method of claim 1,wherein the hydrogen gas has a first temperature, wherein theorthohydrogen-rich hydrogen gas has a second temperature greater thanthe first temperature, wherein the parahydrogen-rich hydrogen gas has athird temperature less than the first temperature.
 12. A methodcomprising: transferring hydrogen gas into a proximal end of a vortextube, at least a portion of an interior wall of the vortex tubecomprising a catalyst, wherein the hydrogen gas comprises orthohydrogenand parahydrogen; flowing the hydrogen gas toward a distal end of thevortex tube, the hydrogen gas rotating within the vortex tube as thehydrogen gas flows toward the distal end; and reacting at least aportion of the hydrogen gas with the catalyst such that at least aportion of the hydrogen gas converts to liquid hydrogen.
 13. The methodof claim 12, wherein the catalyst comprises ruthenium, copper, platinum,palladium, manganese, ferric oxide, silver, a rare earth metal, or acombination thereof.
 14. The method of claim 12, wherein the liquidhydrogen comprises more parahydrogen than orthohydrogen by mass.
 15. Themethod of claim 12, further comprising: transferring a remaining portionof the hydrogen gas out the distal end of the vortex tube.
 16. A devicecomprising: a vortex tube; an inlet disposed on a first end of thevortex tube; a catalyst coating at least a portion of an interior wallof the vortex tube; a first outlet disposed on a second end of thevortex tube, wherein the first outlet comprises an opening on theperimeter of the second end of the vortex tube and a stopper disposed atthe center of the second end of the vortex tube; and a second outletdisposed on the first end of the vortex tube.
 17. The device of claim16, wherein the catalyst comprises ruthenium, copper, platinum,palladium, manganese, ferric oxide, silver, a rare earth metal, or acombination thereof.
 18. The device of claim 16, wherein the catalystcomprises a chemical compound that catalyzes the conversion ofparahydrogen to orthohydrogen.
 19. The device of claim 16, furthercomprising: insulation disposed around at least a portion of an exteriorof the vortex tube.
 20. The device of claim 16, further comprising: aplurality of grooves disposed in the interior wall of the vortex tube.